Hi samo, most of your numbers look pretty good. At idle I shoot for somewhere between 13.9-14.2. The gray color is probably caused by your 12-13 afr at idle. Checking spark plugs on turbo engines is something you should due often. The heat range on your plug so far looks good, but you have not gone to full boost. The white porcelain doesn't have shiny metallic specks, but that can change at any time. Are your plugs new? They don't appear to be. Anyway you need to clean the ground straps to bare metal so you can see the heat mark on them to determine more accurately if the plug might be to hot for full boost. Be sure to put anti-seize on the threads.
I know every project has a budget, however with a turbo having an EGT and Wideband are extremely valuable. Turbo engines are like an addiction. It is easy to keep wanting a little more. Best to have a system that tells you when you are asking for too much.
Have enjoyed reading your post. Thank you for including us in the process.